Organic light emitting display apparatus

ABSTRACT

An organic light emitting display apparatus including a substrate including a plurality of pixel areas; a pixel electrode on the substrate; an opposite electrode on the pixel electrode, the opposite electrode transmitting light; an organic light emitting layer between the pixel electrode and the opposite electrode, the organic light emitting layer emitting a first light toward the opposite electrode; a light emitting layer on the opposite electrode, the light emitting layer absorbing a portion of the first light and emitting a second light; and a sealing layer on the light emitting layer, the sealing layer sealing the pixel electrode, the opposite electrode, the organic light emitting layer, and the light emitting layer.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuation application based on pending application Ser. No.15/439,602, filed Feb. 22, 2017, which in turn is a continuation of Ser.No. 14/933,856, filed Nov. 5, 2015, now U.S. Pat. No. 9,583,727 B2,issued Feb. 28, 2017, which in turn is a continuation of Ser. No.14/446,746, filed Jul. 30, 2014, now U.S. Pat. No. 9,184,403 B2 issuedNov. 10, 2015, the entire contents of which is hereby incorporated byreference.

Korean Patent Application No. 10-2013-0127431, filed on Oct. 24, 2013,in the Korean Intellectual Property Office, and entitled: “ORGANIC LIGHTEMITTING DISPLAY APPARATUS,” is incorporated by reference herein in itsentirety.

BACKGROUND 1. Field

Embodiments relate to an organic light emitting display apparatus.

2. Description of the Related Art

An organic light emitting display apparatus includes an organic lightemitting device that may include a hole injection electrode, an electroninjection electrode, and an organic light emitting layer between thehole injection electrode and the electron injection electrode. Forexample, holes and electrons injected into the organic light emittinglayer may be recombined in the organic light emitting layer to generateexcitons, and the organic light emitting device may emit light by theexcitons that return to a ground state from an excited state. Forexample, the organic light emitting display apparatus is a self-emissivedisplay apparatus.

SUMMARY

Embodiments are directed to an organic light emitting display apparatus.

The embodiments may be realized by providing an organic light emittingdisplay apparatus including a substrate including a plurality of pixelareas; a pixel electrode on the substrate; an opposite electrode on thepixel electrode, the opposite electrode transmitting light; an organiclight emitting layer between the pixel electrode and the oppositeelectrode, the organic light emitting layer emitting a first lighttoward the opposite electrode; a light emitting layer on the oppositeelectrode, the light emitting layer absorbing a portion of the firstlight and emitting a second light; and a sealing layer on the lightemitting layer, the sealing layer sealing the pixel electrode, theopposite electrode, the organic light emitting layer, and the lightemitting layer.

The light emitting layer may include at least one of an organic lightemitting material, a phosphor, or a quantum dot.

The light emitting layer may include the phosphor, the phosphorincluding at least one of a nano-phosphor, a silicate phosphor, anitride phosphor, or a sulfide phosphor.

The light emitting layer may include the quantum dot, the quantum dotincluding at least one of a CdSe core/ZnS shell, a CdSe core/CdS shell,or a InP core/ZnS shell.

The second light may have no directivity.

The first light may include a first incident light that is incident onthe light emitting layer in a direction that is perpendicular to aninterface between the organic light emitting layer and the lightemitting layer, and a second incident light that is incident on thelight emitting layer in a direction that is inclined with respect to theinterface, and the second light may include a first output light that isemitted in response to the first incident light, and a second outputlight that is emitted in response to the second incident light.

The first output light may have a wavelength band that is red shiftedwhen compared to the first incident light, and the second output lightmay have a wavelength band that is red shifted when compared to thesecond incident light.

A difference in a wavelength band between the second incident light andthe second output light may be greater than a difference in a wavelengthband between the first incident light and the first output light.

A difference in a peak wavelength between the second incident light andthe second output light may be greater than a difference in a peakwavelength between the first incident light and the first output light.

A difference in a peak wavelength between a front light constituting aportion of the second light that is obtained from the first incidentlight and an inclined light constituting a remaining portion of thesecond light that is obtained from the second incident light may besmaller than a difference in peak wavelength between the first incidentlight and the second incident light.

The pixel areas may include a red pixel area, a green pixel area, and ablue pixel area, the organic light emitting layer may include a firstorganic light emitting layer in the red pixel area, a second organiclight emitting layer in the green pixel area, and a third organic lightemitting layer in the blue pixel area, and the light emitting layer mayinclude a first light emitting layer in the red pixel area, a secondlight emitting layer in the green pixel area, and a third light emittinglayer in the blue pixel area.

The first organic light emitting layer may include a material that emitslight having a red color, the first organic light emitting layer havinga quantum efficiency that compensates for a color shift caused by a sideviewing angle of the red color, the second organic light emitting layermay include a material that emits light having a green color, the secondorganic light emitting layer having a quantum efficiency thatcompensates for a color shift caused by a side viewing angle of thegreen color, and the third organic light emitting layer may include amaterial that emits light having a blue color, the third organic lightemitting layer having a quantum efficiency that compensates for a colorshift caused by a side viewing angle of the blue color.

The first, second, and third organic light emitting layers may include amaterial emitting a blue color, the first light emitting layer may havea quantum efficiency that compensates for a blue color shift caused by aside viewing angle, the second light emitting layer may have a quantumefficiency that compensates for the blue color shift and a wavelengthdifference between red and green colors, and the third light emittinglayer may have a quantum efficiency that compensates for the blue colorshift and a wavelength difference between the red and blue colors.

The pixel electrode may include a reflective electrode and atransmissive electrode.

The reflective electrode may include Ag, Mg, Al, Pt, Pd, Au, Ni, Nd, Ir,Cr, or a compound thereof, and the transmissive electrode may include atleast one selected from the group of indium tin oxide (ITO), indium zincoxide (IZO), zinc oxide (ZnO), indium oxide (In₂O₃), indium galliumoxide (IGO), or aluminum zinc oxide (AZO).

The opposite electrode may include Li, Ca, LiF/Ca, LiF/Al, Al, Ag, Mg,or a compound thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

Features will be apparent to those of skill in the art by describing indetail exemplary embodiments with reference to the attached drawings inwhich:

FIG. 1 illustrates a cross-sectional view showing an organic lightemitting display apparatus according to an exemplary embodiment;

FIG. 2 illustrates a cross-sectional view showing three pixel areas ofthe organic light emitting display apparatus of FIG. 1;

FIG. 3 illustrates a view showing a light emission mechanism of a secondlight emitted from a light emitting layer;

FIG. 4A illustrates a graph showing an intensity of a first incidentlight as a function of a wavelength of the first incident light;

FIG. 4B illustrates a graph showing an intensity of a second incidentlight as a function of a wavelength of the second incident light;

FIG. 4C illustrates a graph showing intensities of the first and secondincident lights;

FIG. 5A illustrates a graph showing intensities of a first partiallight, a first output light, and a front light obtained by mixing thefirst partial light and the first output light;

FIG. 5B illustrates a graph showing intensities of a second partiallight, a second output light, and an inclined light obtained by mixingthe second partial light and the second output light; and

FIG. 5C illustrates a graph showing the front light of FIG. 5A and theinclined light of FIG. 5B.

DETAILED DESCRIPTION

Example embodiments will now be described more fully hereinafter withreference to the accompanying drawings; however, they may be embodied indifferent forms and should not be construed as limited to theembodiments set forth herein. Rather, these embodiments are provided sothat this disclosure will be thorough and complete, and will fullyconvey exemplary implementations to those skilled in the art.

In the drawing figures, the dimensions of layers and regions may beexaggerated for clarity of illustration. Like reference numerals referto like elements throughout.

It will be understood that when an element or layer is referred to asbeing “on”, “connected to” or “coupled to” another element or layer, itcan be directly on, connected or coupled to the other element or layeror intervening elements or layers may be present. In contrast, when anelement is referred to as being “directly on,” “directly connected to”or “directly coupled to” another element or layer, there are nointervening elements or layers present. Like numbers refer to likeelements throughout. As used herein, the term “and/or” includes any andall combinations of one or more of the associated listed items.

It will be understood that, although the terms first, second, etc. maybe used herein to describe various elements, components, regions, layersand/or sections, these elements, components, regions, layers and/orsections should not be limited by these terms. These terms are only usedto distinguish one element, component, region, layer or section fromanother region, layer or section. Thus, a first element, component,region, layer or section discussed below could be termed a secondelement, component, region, layer or section without departing from theteachings of the present invention.

Spatially relative terms, such as “beneath”, “below”, “lower”, “above”,“upper” and the like, may be used herein for ease of description todescribe one element or feature's relationship to another element(s) orfeature(s) as illustrated in the figures. It will be understood that thespatially relative terms are intended to encompass differentorientations of the device in use or operation in addition to theorientation depicted in the figures. For example, if the device in thefigures is turned over, elements described as “below” or “beneath” otherelements or features would then be oriented “above” the other elementsor features. Thus, the exemplary term “below” can encompass both anorientation of above and below. The device may be otherwise oriented(rotated 90 degrees or at other orientations) and the spatially relativedescriptors used herein interpreted accordingly.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting. As used herein, thesingular forms, “a”, “an” and “the” are intended to include the pluralforms as well, unless the context clearly indicates otherwise. It willbe further understood that the terms “includes” and/or “including”, whenused in this specification, specify the presence of stated features,integers, steps, operations, elements, and/or components, but do notpreclude the presence or addition of one or more other features,integers, steps, operations, elements, components, and/or groupsthereof.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this application belongs. It willbe further understood that terms, such as those defined in commonly useddictionaries, should be interpreted as having a meaning that isconsistent with their meaning in the context of the relevant art andwill not be interpreted in an idealized or overly formal sense unlessexpressly so defined herein.

FIG. 1 illustrates a cross-sectional view showing an organic lightemitting display apparatus 100 according to an exemplary embodiment.FIG. 2 illustrates a cross-sectional view showing three pixel areas ofthe organic light emitting display apparatus 100 of FIG. 1.

Referring to FIGS. 1 and 2, the organic light emitting display apparatus100 may include a substrate 120, a pixel electrode 140, an organic lightemitting layer 150, an opposite electrode 160, a light emitting layer170, and a sealing layer 180.

The substrate 120 may be a flexible substrate. For example, thesubstrate 120 may include a plastic material having high thermalresistance and high durability, such as polyethylene terephthalate,polyethylene naphthalate, polycarbonate, polyarylate, polyetherimide,polyethersulfone, polyimide, or the like. In an implementation, thesubstrate 120 may include, e.g., a metal material or a glass material.

A device/line layer 130 may be disposed on the substrate 120, and mayinclude a driving thin film transistor TFT connected to the pixelelectrode 140, a switching thin film transistor (not shown), acapacitor, and lines (not shown). The lines may be connected between thedriving thin film transistor, the switching thin film transistor, andthe capacitor.

The driving thin film transistor TFT may include an active layer 131, agate electrode 133, a source electrode 135 a, and a drain electrode 135b.

A barrier layer (not shown) may be provided between the substrate 120and the device/line layer 130 to help prevent a foreign substance, e.g.,moisture, oxygen, or the like, from entering into the organic lightemitting layer 150 after passing through the substrate 120.

The organic light emitting display apparatus 100 may include a pluralityof pixel areas PA1, PA2, and PA3, and a pixel definition layer PDL maybe between the pixel areas PA1, PA2, and PA3. The pixel areas PA1, PA2,and PA3 may include, e.g., a first pixel area PA1 emitting a red light,a second pixel area PA2 emitting a green light, and a third pixel areaPA3 emitting a blue light.

The pixel electrode 140 may be on the device/line layer 130. The pixelelectrode 140 may correspond to each of the first, second, and thirdpixel areas PA1, PA2, and PA3. For example, the first pixel area PA1 mayinclude a pixel electrode 140, the second pixel area PA2 may include apixel electrode 140, and the third pixel area PA3 may include a pixelelectrode 140. The opposite electrode 160 may be on the pixel electrode140, and the organic light emitting layer 150 may be between the pixelelectrode 140 and the opposite electrode 160.

In an implementation, the pixel electrode 140 may serve as an anode, andthe opposite electrode 160 may serve as a cathode. In an implementation,and according to a driving method of the organic light emitting displayapparatus 100, the pixel electrode 140 may serve as the cathode and theopposite electrode 160 may serve as the anode. Holes and electrons,which may be injected into the organic light emitting layer 150 from thepixel electrode 140 and the opposite electrode 160, may be recombined inthe organic light emitting layer 150 to generate excitons. The organiclight emitting layer 150 may emit a first light when the excitons returnto a ground state from an excited state.

FIG. 2 illustrates an example of a structure of the device/line layer130. For example, an arrangement of the active layer 131, the gateelectrode 133, the source electrode 135 a, and the drain electrode 135 bmay be varied. For example, as opposed to the gate electrode 133 beingon the active layer 131 (as shown in FIG. 2), in an implementation, thegate electrode 133 may be under the active layer 131.

The pixel electrode 140 may include, e.g., a reflective electrode 140 aand a transmissive electrode 140 b. The reflective electrode 140 a mayinclude, e.g., Ag, Mg, Al, Pt, Pd, Au, Ni, Nd, Ir, Cr, or a compoundthereof. The transmissive electrode 140 b may be transparent orsemi-transparent, and may include, e.g., at least one selected from thegroup of indium tin oxide (ITO), indium zinc oxide (IZO), zinc oxide(ZnO), indium oxide (In₂O₃), indium gallium oxide (IGO), or aluminumzinc oxide (AZO).

The opposite electrode 160 may be transparent or semi-transparent, andmy include, e.g., a metal thin layer having a low work function. Theopposite electrode 160 may include, e.g., Li, Ca, LiF/Ca, LiF/Al, Al,Ag, Mg, or a compound thereof. In an implementation, the oppositeelectrode 160 may further include a material used to form a transparentelectrode, e.g., ITO, IZO, ZnO, In₂O₃, or the lie, which may be disposedon the metal thin layer. The opposite electrode 160 may transmit lightemitted from the organic light emitting layer 150.

The organic light emitting layer 150 may include, e.g., a low molecularorganic material or a high molecular organic material. The organic lightemitting layer 150 may include, e.g., first, second, and third organiclight emitting layers 151, 152, and 153 in the first, second, and thirdpixel areas PA1, PA2, and PA3, respectively.

An intermediate layer, e.g., a hole transport layer, a hole injectionlayer, an electron transport layer, an electron injection layer, or thelike, may be selectively disposed between the pixel electrode 140 andthe opposite electrode 160, in addition to the organic light emittinglayer 150.

Light emitted from the organic light emitting layer 150 may be reflectedby the pixel electrode 140 and may exit or be transmitted through theopposite electrode 160. For example, the organic light emitting displayapparatus 100 may be a front surface light emitting type organic lightemitting display apparatus 100.

The sealing layer 180 may be on the light emitting layer 170 to helpprevent the pixel electrode 140, the organic light emitting layer 150,the opposite electrode 160, and the light emitting layer 170 from beingexposed to external moisture and/or oxygen, e.g., the sealing layer 180may seal the pixel electrode 140, the organic light emitting layer 150,the opposite electrode 160, and the light emitting layer 170.

The light emitting layer 170 may be on the opposite electrode 160. Thelight emitting layer 170 may include, e.g., first, second, and thirdlight emitting layers 171, 172 and 173 in the first, second, and thirdpixel areas PA1, PA2, and PA3, respectively.

The light emitting layer 170 may absorb a portion of a first light(emitted from the organic light emitting layer 150) to generate a secondlight.

The light emitting layer 170 may include a light emitting material,e.g., an organic light emitting material, a phosphor, or a quantum dot.The phosphor may include, e.g., at least one of a nano-phosphor, asilicate phosphor, a nitride phosphor, or a sulfide phosphor. Thequantum dot may include, e.g., at least one of CdSe core/ZnS shell, CdSecore/CdS shell, and InP core/ZnS shell.

When an excited or first light, e.g., a blue excited light (having ahigh energy level that causes a light emission phenomenon), is incidentto or on the light emitting layer 170, the second light (having along-wavelength band or low energy wavelength band, which is inproportion to absorbancy and light emission quantum efficiency of thelight emitting layer 170), may be generated by or in response to theexcited or first light.

The second light emitted from the light emitting layer 170 may have nodirectivity.

FIG. 3 illustrates a view showing a light emission mechanism of thesecond light emitted from the light emitting layer 170. FIG. 3 shows thepixel electrode 140, the organic light emitting layer 150, the oppositeelectrode 160, and the light emitting layer 170.

Referring to FIG. 3, the first light may include, e.g., an incidentlight directly exiting from the front surface of the organic lightemitting layer 150 or exiting from the front surface of the organiclight emitting layer 150 after being reflected by the pixel electrode140 and the opposite electrode 160. The incident light may include,e.g., a first incident light L1 that is incident to or on the lightemitting layer 170 in a direction that is substantially vertical orperpendicular to an interface between layers (e.g., between the oppositeelectrode 160 and the light emitting layer 170), and a second incidentlight L2 that is incident to or on the light emitting layer 170 in adirection that is inclined relative to the interface.

The structure in which the pixel electrode 140 faces the oppositeelectrode 160 and the organic light emitting layer 150 is between thepixel electrode 140 and the opposite electrode 160 corresponds to ametal-insulator-metal cavity model. The first light generated in themetal-insulator-metal cavity model may have a wavelength in accordancewith or determined by an output angle thereof. For example, as ahorizontal component of the first light becomes greater than a verticalcomponent of the first light, or as the output angle becomes large, thewavelength of the first light may become shorter and may move or shiftto a blue wavelength side. A blue color shift may occur in the imageperceived by the user as the viewing angle becomes large.

The first incident light L1 may be incident to or on the light emittinglayer 170, and a first partial light L1-1 (corresponding to a portion ofthe first incident light L1) may exit from the front surface (e.g., maybe transmitted) at an output angle that is the same as the incidentangle of the first incident light L1 after passing through the lightemitting layer 170. A remaining portion of the first incident light L1may be absorbed by the light emitting layer 170. The light emittinglayer 170 may emit a first output light L3 on the basis of or inresponse to the absorbed remaining portion of the first incident lightL1. The first output light L3 may have no directivity.

The second incident light L2 may be incident to or on the light emittinglayer 170, and a second partial light L2-1 (corresponding to a portionof the second incident light L2) may exit from the front surface (e.g.,may be transmitted) at an output angle that is the same as an incidentangle of the second incident light L2 after passing through the lightemitting layer 170. A remaining portion of the second incident light L2may be absorbed by the light emitting layer 170. The light emittinglayer 170 may emit a second output light L4 on the basis of or inresponse to the absorbed remaining portion of the second incident lightL2. The second output light L4 may have no directivity.

The wavelength of the second incident light L2 may be shorter than thewavelength of the first incident light L1, and the first incident lightL1 may include more light having high energy (e.g., that causes a lightemission phenomenon of the light emitting layer 170) than that of thesecond incident light L2. For example, the second incident light L2 mayhave a constant incident angle, and thus the second incident light L2may pass through the light emitting layer 170 through a light path thatis longer than a light path (through the light emitting layer) of thefirst incident light L1 that is incident perpendicular to the interfaceof the light emitting layer 170 and another layer. Accordingly, thelight emitting layer 170 may absorb more of the second incident light L2than the first incident light L1.

The first and second output lights L3 and L4 may each have a wavelengthband shifted to the red color, when respectively compared to the firstand second incident lights L1 and L2.

A difference in the wavelength band between the second incident light L2and the second output light L4 may be greater than a difference in thewavelength band between the first incident light L1 and the first outputlight L3. This may be because the output lights L3 and L4 may have thewavelength that is more shifted to the red color than the incidentlights L1 and L2, as the amount of the incident lights L1 and L2 that isabsorbed by the light emitting layer 170 is increased, and the secondincident light L2 is absorbed to a greater degree by the light emittinglayer 170 than the first incident light L1.

The light emitting layer 170 may allow the wavelength band of the secondoutput light L4 to be shifted to a greater degree to the red color thanthe first output light L3. Thus, the blue color shift in the imageperceived by the user may be improved, e.g., may be compensated for. Forexample, the image viewed from a side or wide viewing angle of thedisplay may appear to be the same (e.g., same colors) as the imageviewed from the front of the display.

In the present exemplary embodiment, the first, second, and thirdorganic light emitting layers 151, 152, and 153 may include, e.g., red,green, and blue phosphor materials, respectively. In an implementation,the first, second, and third light emitting layers 171, 172, and 173 mayinclude different materials from each other. For example, the first,second, and third light emitting layers 171, 172, and 173 may have thequantum efficiency that compensates for the color shift due to the sideviewing angle in red, green, and blue colors, respectively.

In an implementation, all of the first, second, and third organic lightemitting layers 151, 152, and 153 may include the blue phosphormaterial. For example, the first light emitting layer 171 may have thequantum efficiency that compensates for the blue color shift caused bythe side viewing angle, the second light emitting layer 172 may have thequantum efficiency that compensates for the blue color shift and thewavelength difference between the red and green colors, and the thirdlight emitting layer 173 may have the quantum efficiency thatcompensates for the blue color shift and the wavelength differencebetween the red and blue colors.

FIG. 4A illustrates a graph showing an intensity of the first incidentlight as a function of the wavelength of the first incident light, FIG.4B illustrates a graph showing an intensity of the second incident lightas a function of the wavelength of the second incident light, and FIG.4C illustrates a graph showing the intensities of the first and secondincident lights.

FIG. 5A illustrates a graph showing intensities of the first partiallight, the first output light, and a front light obtained by mixing thefirst partial light and the first output light, FIG. 5B illustrates agraph showing intensities of the second partial light, the second outputlight, and an inclined light obtained by mixing the second partial lightand the second output light, and FIG. 5C illustrates a graph showing thefront light shown in FIG. 5A and the inclined light shown in FIG. 5B.

Hereinafter, a wavelength value at a maximum intensity is referred to asa peak wavelength in FIGS. 4A to 4C and 5A to 5C.

Referring to FIGS. 3, 4A, and 4B, the wavelength band of the secondincident light L2 may be more biased to a shorter wavelength, e.g.,blue, than that of the first incident light L1. Thus, if the lightemitting layer 170 (refer to FIGS. 1 to 3) were to be omitted, the bluecolor shift could occur in the image perceived by the user according tothe viewing angle, e.g., when viewing from the side. Referring to FIG.4C, a first difference W1 may exist between the peak wavelength of thefirst incident light L1 and the peak wavelength of the second incidentlight L2. For example, the first difference W1 may be about 10 nm.

Referring to FIGS. 3, 4A, and 5A, the peak wavelength of the firstpartial light L1-1 may be the same as the peak wavelength of the firstincident light L1. The peak wavelength of the first output light L3 maybe more biased to a longer wavelength, e.g., red, than the peakwavelength of the first incident light L1. A second difference W2 mayexist between the peak wavelength of the first partial light L1-1 andthe peak wavelength of the first output light L3.

Referring to FIGS. 3, 4B, and 5B, the peak wavelength of the secondpartial light L2-1 may be the same as the peak wavelength of the secondincident light L2. The peak wavelength of the second output light L4 maybe more biased to a longer wavelength, e.g., red, than the peakwavelength of the second incident light L2. A third difference W3 mayexist between the peak wavelength of the second partial light L2-1 andthe peak wavelength of the second output light L4. The third differenceW3 may be greater than the second difference W2. This means that thesecond output light L4 may be more shifted to the red color than thefirst output light L1.

Referring to FIGS. 3, 4C, and 5C, a fourth difference W4 may existbetween the peak wavelength of the front light L5 (obtained by mixing orcombining the first partial light L1-1 and the first output light L3)and the peak wavelength of the inclined light L6 (obtained by mixing orcombining the second partial light L2-1 and the second output light L4).The front light L5 may correspond to or constitute a portion of thesecond light that is obtained from or in response to the first incidentlight L1, and the inclined light L6 may correspond to or constitute aremaining portion of the second light obtained from or in response tothe second incident light L2. In an implementation, the fourthdifference W4 may be, e.g., about 2 nm. The fourth difference W4 may besmaller than the first difference W1. Thus, the blue color shiftphenomenon in the image perceived by the user according to the viewingangle may be improved by the light emitting layer 170.

By way of summation and review, an organic light emitting displayapparatus has been spotlighted as a next generation display device forits superior brightness and viewing angle. The organic light emittingdisplay apparatus does not need to include a separate light source, andit has thin thickness and light weight. In addition, the organic lightemitting display apparatus may have desirable properties, e.g., fastresponse speed, low power consumption, high brightness, etc.

A color shift may occur at a side viewing angle of an organic lightemitting display apparatus due to an output angle of light exiting fromthe organic light emitting device.

The embodiments may provide an organic light emitting display apparatusthat is capable of preventing a color shift from occurring at a side orwide viewing angle.

For example, the blue color shift phenomenon in the image perceived bythe user according to the side viewing angle may be improved.

Example embodiments have been disclosed herein, and although specificterms are employed, they are used and are to be interpreted in a genericand descriptive sense only and not for purpose of limitation. In someinstances, as would be apparent to one of ordinary skill in the art asof the filing of the present application, features, characteristics,and/or elements described in connection with a particular embodiment maybe used singly or in combination with features, characteristics, and/orelements described in connection with other embodiments unless otherwisespecifically indicated. Accordingly, it will be understood by those ofskill in the art that various changes in form and details may be madewithout departing from the spirit and scope of the present invention asset forth in the following claims.

What is claimed is:
 1. A display apparatus, comprising: a substrateincluding a plurality of pixel areas; a pixel electrode on thesubstrate; an opposite electrode on the pixel electrode; a main lightemitting layer between the pixel electrode and the opposite electrode,the main light emitting layer emitting a first light; and a sub lightemitting layer on the substrate, wherein the sub light emitting layerabsorbs a portion of the first light and emits a second light.
 2. Thedisplay apparatus as claimed in claim 1, wherein the sub light emittinglayer includes at least one of an organic light emitting material, aphosphor, or a quantum dot.
 3. The display apparatus as claimed in claim2, wherein the sub light emitting layer includes the quantum dot, thequantum dot including at least one of a CdSe core/ZnS shell, a CdSecore/CdS shell, or an InP core/ZnS shell.
 4. The display apparatus asclaimed in claim 1, wherein: the pixel areas include a red pixel area, agreen pixel area, and a blue pixel area, the main light emitting layerincludes a first organic light emitting layer in the red pixel area, asecond organic light emitting layer in the green pixel area, and a thirdorganic light emitting layer in the blue pixel area, and the sub lightemitting layer includes a first light emitting layer in the red pixelarea, a second light emitting layer in the green pixel area, and a thirdlight emitting layer in the blue pixel area.
 5. The display apparatus asclaimed in claim 4, wherein: the first organic light emitting layerincludes a material that emits light having a red color, the secondorganic light emitting layer includes a material that emits light havinga green color, and the third organic light emitting layer includes amaterial that emits light having a blue color.
 6. The display apparatusas claimed in claim 4, wherein: the first, second, and third organiclight emitting layers include a material emitting a blue color.
 7. Thedisplay apparatus as claimed in claim 6, wherein: a light emitted fromthe first organic light emitting layer and passing through the firstlight emitting layer has a red color, a light emitted from the secondorganic light emitting layer and passing through the second lightemitting layer has a green color, and a light emitted from the thirdorganic light emitting layer and passing through the third lightemitting layer has a blue color.
 8. The display apparatus as claimed inclaim 4, wherein the second light has no directivity.
 9. The displayapparatus as claimed in claim 4, wherein: the first light includes: afirst incident light that is incident on the sub light emitting layer ina direction that is perpendicular to an interface between the main lightemitting layer and the sub light emitting layer, and a second incidentlight that is incident on the sub light emitting layer in a directionthat is inclined with respect to the interface, and the second lightincludes: a first output light that is emitted in response to the firstincident light, and a second output light that is emitted in response tothe second incident light.
 10. The display apparatus as claimed in claim9, wherein: the first output light has a wavelength band that is redshifted when compared to the first incident light, and the second outputlight has a wavelength band that is red shifted when compared to thesecond incident light.
 11. The display apparatus as claimed in claim 9,wherein a difference in a wavelength band between the second incidentlight and the second output light is greater than a difference in awavelength band between the first incident light and the first outputlight.
 12. The display apparatus as claimed in claim 9, wherein adifference in a peak wavelength between the second incident light andthe second output light is greater than a difference in a peakwavelength between the first incident light and the first output light.13. The display apparatus as claimed in claim 9, wherein a difference ina peak wavelength between a front light constituting a portion of thesecond light that is obtained from the first incident light and aninclined light constituting a remaining portion of the second light thatis obtained from the second incident light is smaller than a differencein peak wavelength between the first incident light and the secondincident light.
 14. The display apparatus as claimed in claim 1, whereinthe sub light emitting layer is disposed on the opposing electrode.